1. Field of the Invention
The present invention relates to non-toxic antifouling coating compositions free from toxic materials, and more particularly to coating compositions which can be applied to underwater structures such as ships, port facilities, buoys, pipelines, bridges, water conduit raceway tubes in power plants, submarine stations, submarine oil field excavation facilities, cultivating fishing nets, stationary fishing nets and the like. The compositions provide an antifouling film on the surface of the underwater structures which prevents underwater organisms from adhering and growing on the surfaces of the structures over a long period of time.
2. Description of the Prior Art
A large number of organisms such as barnacles, ascidian, serupulas, fresh- and salt-water mussels, polyzoan, green algae, sea lettuce and the like live in the waters of the sea, rivers, lakes and swamps. These plants and animals cause various types of damage to the surfaces of structures that are submerged in or splashed with these waters.
In order to prevent the underwater organisms from adhering to the underwater structures and growing thereon, antifouling coating compositions have previously been prepared incorporating toxic antifouling agents such as organotin compounds. While the use of such antifouling coating compositions could almost entirely prevent the underwater organisms from adhering to underwater structures and growing thereon, the use of the toxic antifouling agents is undesirable from the standpoints of environmental safety and hygiene.
In order to solve the above problems, various non-toxic antifouling coating compositions have previously been proposed. For example, U.S. Pat. Nos. 4,025,693 and 5,218,059 disclose non-toxic antifouling coating compositions which are prepared using a silicone rubber alone or as a mixture with a silicone oil. The use of a silicone rubber in combination with a silicone oil markedly improved antifouling properties of the coatings compared with the use of a silicone rubber alone. However, the use of the silicone rubber in combination with the silicone oil was not entirely satisfactory in antifouling durability over a long period of time. Hence, further improvement in antifouling properties and the durability of these properties has been sought.